Dynamometer.



PATENTED MAY 19, 1908.

J. B. WEBB. DYNAMOMETER.

APPLICATION FILED MAR. 27, 1907.

('-T0 PROPELLER JOHN BURKITT WEBB, or GLENRIDGE, NEW JERSEY.

DYNAMOMETER.

Specification of Letters Patent.

Patented May 19, 1908;

Application filed March 27, 1907. Serial No. 864,921.

To all whom it may concern:

Be it known that 1, JOHN BiIRKIT'r WEBB,

a citizen of the United States, and a resident of Glenridge, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Dynamometers, of which the following is a specificat1on.- I

invention relates to dynamometers or devices adapted to measure or register power,

and particularly to a device adapted to measure or register the power transmitted through a rotating shaft. i

For this purpose my invention consists essentially of means to determine the angle of twist or torsion and the corresponding speed of a certain length of said shaft when under stress, and thereby-the power transmitted.

The nature of my invention will be best understood in connection with the accom- 1 corresponding parts throughout the several wit views.

' In the drawings, 10 is a shaft preferably hollow, which transmits power from, for example, a turbine to a propeller (neither being shown in the drawings). This shaft-runs in suitable bearings (not shown) and is usually of several sections bolted together in the usual manner by suitable couplings as the coupling 11 which is made in this instance somewhat heavier and shaped to accommodate the apparatus. 7

Within the hollow shaft 10 is a second and smaller shaft 12 supported at intervals by suitable bearings and at the inner or turbine end by the ball bearing .journal 13. The outer or ropeller end is rigidly secured to the hollow s aft 10 as shown, thereby causing the entire shaft 12 to turn with the said shaft 10 To the inner brturbine end of this shaft is fastened a yoke 14 provided with two arms 15 projecting through suitable slots 16 in the cou ling 11, so that connection may be made l fsaid shaft from the outside. Two similar armature wheels 17 and 18, preferably shaped support of the frame 25.

crown wheels, havin teeth of suitable shape for their purpose an of a number depending somewhat on the speed of the shaft 10, are mounted on the said shaft 10 as shown. They are preferably made in two'halves and with sleeves 19 and 20 of some length, fitting the shaft 10 so that they may be readily ut on the shaft and bolted together tight. he Wheel 17 is fitted to revolve freely upon the shaft 10, and its position on said shaft is governed by the yoke I l-through the two removable studs 21 which are screwed into the arms 15 of said yoke, and connect the wheel 17 thereto. Thewlieel 18 is fittedto pinch the shaft 10 at (at) and runs with it.

The sleeves 19 and 20 are rovided with lugs 22, 23, so that the two s eeves may be fastened together by bolts. In front of each of the crown wheels are one or more similar, permanent magnets 24 with tele hone coils and mounted on the frames 25. nets are adjustable endwise in their supports 26, by'means of spiral springs; which push the magnets toward the wheels and screws which draw them back, the adjustment being made by turning the milled heads 27. The ends of the properly shaped cores of these magnets pro ect through therespective supports 26 and stand close in front of the teeth One or more pole of the armature wheels, pieces or armature magnets 28 are mounted on thecrown wheels 17 and 18 on the reverse side, and face other field magnets 29 mounted on a frame 30. The alternating current generators are not necessarily mounted directly uponthe shaft, but may be drivenin any suitable way in connection therewith. The ma nets 24 are adjustable concentrically wit frame 25 is made arc-shaped and graduated as shown, and is concentric with the said shaft and adapted to slide in a similar arc.-

The adjustments of the frames are made through turningthe milled heads 31 carrying pinions (not shown) engaging with concealed curved racks (also not shown) of the said frames. By tightening the bolts 32 the arc-shaped pieces may be clamped together and motion of the magnet frames prevented. The magnets 24 are mounted in their respective supports 26, which supports are also notched at the top, as shown, to hold a reading microscope. The two magnets 24 shown in drawings are so mounted on the magnet frames 25 that when one armature tooth arrives or the shaft 10. A portion of the hese magso t at they act as one magnet.

stands exactly opposite one magnet, another tooth is exactly in front of the other. The ma ets on one magnet frame are connected If only one magnet be mounted on a frame its support must be more accurately set with-respect to the center of the shaft 10, whereasiwo or more magnets tend tocorrect any error due to an eccentricity of the magnet frame with respect to the shaft center. ma ets 24 are connected in series and the lea s 33 therefrom connected to the telephone receiver 34. The leads 35 and 36 from the two sets'. of magnets 29 are connected withthe recording device 37. This recording devicev may indicate and record either potential, current or phase.

Fig. 4 illustrates an electrically vibrated tuning fork 38 of variable pitch adjustable by the graduated milled head 39 previously calibrated, and is used in conjunction with the telephone receiver 34 for instantaneously and accurately determining the speed, as hereinafter set forth.

The theory and operation of-m dynamometer is as follows It is well l m when power is transmitted through a shaft, the said shaft is twisted, and that the degree .of this twisting is a function of the power transmitted. If now, a certain length of the shaft has been calibrated; or a calibration determined by calculation, so that the number of degrees twist is known which will .be

produced by a given moment; it remains only, in order to arrive at a knowledge of the power being transmitted, to providesome accurate means whereby, while'the shaft is running, this twist can be measured and the correspondings eed'determined.

In order to o tain a considerable lengthof shaft and yet have the 'measuring ap aratus compact and at an accessible point, t e shaft 10 is hollow so that the inner shaft 12 may be inserted as already explained. By this expedient the small inner shaft, fastenedto the shaft 10 at or near the ropeller end, turns with the said shaft 10 but is not twisted. The yoke arms- 15 will therefore move in the slots 16 relatively to the coupling 11. Any twist of the shaft 10 between the point (x) at which the wheel 18 is clamped and the point (y) at which the small. shaft 12 is fastened to the hollow shaft will therefore be shown as so many degrees angular dis lacement or revolution of wheel 17 relatively to wheel'18.

In case the power transmitting shaft is not hollow and therefore no inner shaft can be used, the two wheels 17 and 18. are both ada ted to be rigidlyiattached to the power sha and at as eat a distance apart as possible. placement while running and thereby measure the actual twist of the shaft, I employ the magnets and auxiliary agi iaratus already described. As the teeth 0 t e crown wheels 17 The two sets of own that To readi v determine this angular dis-,

sesmr and 18 revolve in front of the cores'of magnets 24, or the pole ieces 28 revolve in front of the magnets 29, a ternating currents are induced. These currents are combined in a suitable manner, and the former directed as shown in Fig. 1, to a telephone receiver 34 andthe latter to a recording device 37. The currents directed through the telephone re- I ceiver 34 if adjusted to be equal in strengthand opposite in phase, will neutralize each other and no sound will be heard in the telephone receiver. The teeth of both Wheels 17 and 18' then pass their respective electromagnets 24 at the same instant. So soon, however, as the shaft twists, the teeth of one wheel will lag behind those of the other, and the phase is correspondingly altered. A distinct musical tone, whose quality is determined by the number of teeth and other proportions is then emitted by the tele hone receiver 34. To determine this disp acement,

one set of the magnets 24'is now moved concentrically with respect to the shaft 10 by turning the milled head 31 until no sound is heard, thus indicating that the two Wheels are again running in the initial relative positions. The amount of movement required to restore this initial condition is then read off .on the graduatedsupport 25. This is then a measure of the torque, or by suitable graduation may be read directly as horse power transmitted by the shaft per 1000 revolutions. For the purpose of recording these differences, thestronger currents from magnets 29 are directed through the recording device 37.

To obtain an adjustment .for zero I roceed as followsThe ro e'ller is remove or dis' connected from t e s aft 10 so thatthe latter I may be run at full speed without conveying power. Under these conditions the said shaft remains untwisted and the relative po" sitions of the two wheels 17 and 18 will be the same whether the shaft be running or at rest. With the shaft running thus, the frame on which the measurements are to be made and which I designate the measuring frame, is set to zero; and the other or adjusting frame, is setso that the telephone is at zero (emits no sound). The distances of the magnets 24 fromtheir respective wheels areadjusted at the same time, asthe currents induced must have the same intensitfy to bring the telephone to zero. The sha t is then stopped and the adjusting frame. is per manently clamped to it and-the pro eller replaced. The test is now proceede with as reviously explained, using the measuring fi-ame to determine the twist of.',the shaft. When the shaft is not twisted, the telephone 1 "is at zero when the. measuring frame reads twist.

Should it. be inconvenient to remove. thegether.

and the studs 21 are unscrewed so as to disconnect the wheel 17 from the shaft 12. The shaftlO is now run temporarily but does not thereby change the relative positions of the wheels 17 and 18 which are fastened to- The "measurin frame is then set to zero and the adjusting frame set and clamped as before; after which the studs are replaced and the bolts removed from the lugs 22 and 23 so as to make the apparatus read for a test. Should the shaft 10 not be ho low, the greatest accessible length (w z) is chosen and the wheel 17 fitted to be clamped tight to said shaft at (z).

To make the zero adjustment I proceed precisely as before with wheel 17 bolted to wheel 18, after which the shaft is stopped. I then cement or clam four short temporary scales on the teeth 0 the wheels 17'and 18 so thatthey may be read through a reading microscope laid in the notched to s of the magnet supports 26, and record the ourreadings. The wheel 17 is then disconnected from wheel 18 and taken from the shaft and clam ed at (z) The magnet frame is then adj uste so that the microscopes give the same readings as before,the wheel 18 being also again inspected to make sure that no change has taken place. The teeth of both wheels will then be in exactly the same positions relative to their magnetsas they were before. This adjustment, however, will move the ointer away from the zero mark; and it shou d then be set back to zero, and the adjusting frame also set back the same amount. The apparatus is then ready for a test.

If there be any doubt as to the rigidity of the frame of the ship to which the frames 25 are fastened, a frame of wrought iron tubing can be screwed together connecting the two said frames, and one of these frames then disconnected sufficiently from the ships frame.

to make sure that the relative angular position of one of said frames with respect to the other does not change.

The calibration ofthe shaft may be effected eitherbefore or after the installation of. the same, or its strength determined by calculation. The shaft having been calibrated or thecorres onding calculation made, the torque m cot-pounds cogesiponding to the.

scale reading is known, a om it and the speed the horse-power is calculated. The speed may be taken with any suitable speed indicator or recorder operated mechanically by the shaft, or electrically by alternating or other current.

For instantaneous and accurate determination of the speed of the rotating shaft' I prefer to employ the electrically vibrated tuning fork shown in Fig. 4. This fork is of variable pitch adjusted by the graduated milled head reviously calibrated, and is used in conunction with the telephone receiver. Its tone is brought into unison with the telehone tone, and the speed thereby indicated y the reading of the graduated milled head.

I claim:

1. In a dynamometer: a. rotating and twisting shaft; means in operative relation thereto to generate alternating currents of electricity having a phase difference dependent on the twist of said shaft; and indicating means to indicate this phase difference.

2. In a dynamometer: a rotating and twisting shaft; means in operative relation thereto to generate alternating currents of electricity having a phase difference dependent on the twist of said shaft; and indicatim and recordin means to indicate and recor this phase di 'erence.

3. In a dynamometer: a rotating and twisting shaft; two alternating current generators in operative relation thereto togenerate alternating currents of electricity havin a base difference dependent on the twist 0 said shaft; and indicating means to indicate this phase difference.

4. In a dynamometerz a rotatingand twisting shaft;-two alternating current generators operatin in relation to different points of said shaft; means for adjusting, and means formeasuring the position of the fields of said generators.

5. In a dynamometer: 'a rotating 'and twisting shaft; two alternating current generators operating in relation 'to different points of said shaft; means for indicating, means for measuring and means for adjusting the position of a field with reference to its armature when the shaft is at rest.

6. In a dynamometer: a rotating and twisting shaft; two alternating current generators operating in relation thereto; adjustable frames carrying the fields of said generators; and means to adjust said frames.

7. In a dynamometer: a rotating and twisting shaft; two alternatin current generators operating in relation t ereto at different partsof said shaft and having therefore a phase difference de endent on the twist of said shaft; and a te ephone receiver in connection with said alternating current enerators adapted to indicate the said phase ifference.

8. In a dynamometer: 'a rotating and twisting shaft; two alternating current generators operating in'relation thereto at different arts of said'shaft and havin therefore a ase difference dependent on the twist of sai shaft; a telephone receiver in connectionwith said alternating current generators to indicate the said phase difference; and means adapted in conjunction with said telephone recelver to measure the speed of said rotating shaft. J

9. In a dynamometer: a holl w rotating and twisting shaft; an alternating current Signed at New York in the county of New generator driven from one part of said shaft; York and State of New York his 21st dayt ol a second rotating and non-twisting shaft March A. D. 1907. within said hollow shaft, and connected J. BURKITT WEBB.

5 thereto at another sufficiently remote point; Witnesses:

and a second alternating current generator FREDK. F. SoHUETz, driven by said second shaft. SALLY O. YUDIZKY. 

